1. Field of the Invention
The present invention relates to the field of electronic audio/video home entertainment systems. More particularly, the present invention relates to the field of speaker system arrangements for stereo surround sound audio systems.
2. Description of the Prior Art
Home electronic audio/video entertainment systems have become very popular today. Many people have installed complete audio/video systems at their own homes to make so called "home theaters" for enjoying individualized entertainment.
A "home theater" entertainment system typically includes a large screen or projection television (TV) set, a multiplicity of audio/video components and a speaker system. The multiplicity of audio/video components may comprise an audio/video receiver which serves as the control center of all other audio and video components of the entire audio/video system. The audio components may include a compact disc (CD) player, a cassette tape recorder/player, a digital audio tape (DAT) recorder/player, and a turntable. The video components may include a video cassette recorder (VCR) and a laser disc (LD) player.
The speaker system of the home theater system typically includes a right front speaker, a left front speaker and two rear speakers. The term "speaker" used throughout this application does not refer to a single loudspeaker, but rather to a unit of loudspeakers. A "speaker" used in this sense generally comprises three basic parts. The first part includes one or more loudspeaker drivers, such as a "tweeter" which reproduces high frequency sounds, a "midrange" which reproduces mid-frequency sounds, and a "subwoofer" which reproduces low frequency sounds. The second part includes a crossover network which divides the input frequencies into two or more bands for their appropriate drivers. The third part is an acoustic cabinet which houses the loudspeaker drivers. If a driver is mounted at the front side of the cabinet, it is a "frontfiring" driver.
Therefore, in this application the term "speaker" refers to the complete unit including the independent cabinet, in which one or more drivers and crossover networks are installed. The term "driver" then refers to the single loudspeaker driver such as a tweeter, a midrange, a full-range, a woofer and a subwoofer.
For example, a traditional "3-way" speaker has three drivers mounted inside a rectangular box-shaped cabinet. The three drivers may be a tweeter, a midrange or a full range, and a subwoofer or woofer. The physical dimensions of the drivers are often measured by the diameters of their respective diaphragms. For example, in many home entertainment systems, the sizes of tweeters may be between 1/2 and 2 inches, the sizes of midranges or full ranges may be between 31/2 and 6 inches, and the sizes of subwoofers or woofers may be between 6 and 10 inches.
An important aspect of the high and mid-frequency drivers is that they are directional drivers, which means that they must be placed in the direction of the listener. Low frequency drivers are non-directional and may be placed anywhere without reducing their sound qualities. This is because the wavelength of low frequency sound waves are much longer and less likely to encounter interference by furniture or other objects.
Early home stereo systems reproduced a stereo sound effect through two separate channels: a right front channel and a left front channel. The advanced high fidelity (HiFi) home stereo systems now typically reproduce a surround sound effect in four separate channels. Two more channels are provided in addition to the right and left front channels, including a rear surround channel and a center channel. The rear surround channel is used primarily for time-delay surround effect, and the center channel is used primarily for on-screen dialogues. The term "dialogue" is used in the art to describe primarily the sound of human voices such as news announcement, conversations and singing. It may also include other sounds in the same frequency range. Almost all CDs, LDs and DAT music tapes, most VCR movie tapes and audio cassette music tapes, and many TV and radio programs broadcast on network or cable systems are now encoded with all four channels.
In a typical speaker system, the right front speaker is connected to the right front channel of a receiver (or amplifier), the left front speaker is connected to the left front channel of the receiver, and the two rear speakers 26 are connected to the rear surround channel of the receiver. However, the speaker systems of conventional home entertainment systems usually do not have a center channel speaker. Center channel speakers are desirable because they produce much clearer sound effect for dialogue, and deliver more realistic sound effects because the sound is coming from the center where the TV set is placed and from which the sound of dialogue is supposed to emanate.
Prior art inventions have attempted to solve this problem in two basic ways. The first attempt to solve this problem was to use the built-in speaker of the TV set, provided that input terminals for its built-in speaker are incorporated into the TV set. The second way to solve this problem was to use the so-called "phantom" mode available on some models of the receivers. In such "phantom" mode the signal of the center channel is sent to the two front speakers. The two front speakers then reproduce synthesized sound for the non-existing center channel speaker.
It is more desirable today to use independent and separate real center channel speakers because the speakers built into the TV sets usually produce less effective sound effects than separate speakers, and the quality of the synthesized "phantom" sound produced by the front speakers cannot be as good as the quality of the real sound produced by a real center channel speaker. Therefore, it will be very beneficial to design and manufacture an independent center channel speaker which is able to produce high quality sound effects of the center channel of the HiFi surround sound stereo audio systems.